base64 图片读取 开发记录

自己写的方式最后结果，新生成图片打开失败，提示图片错误

try {
    File file = new File("D:\chengdu.jpg");
    FileInputStream in = new FileInputStream(file);
    FileOutputStream out = new FileOutputStream("D:\ceshi.jpg");
    byte[] bytes = new byte[1024];
    int len = -1;
    while((len = in.read(bytes)) != -1) {
//                out.write(bytes, 0, len);
    }
    String cont = EncodeUtils.base64Encode(bytes);
    System.out.println(cont);
    System.out.println(Arrays.toString(bytes));
    
    byte[] ob = EncodeUtils.base64Decode(cont);
    System.out.println(EncodeUtils.base64Encode(ob));
    System.out.println(Arrays.toString(ob));
    
    out.write(ob);
    
    in.close();
    out.close();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

查找资料，换成另一种方式，新生成图片成功

byte[] data = null;
FileInputStream is = null;
try {
    is = new FileInputStream(new File("D:\chengdu.jpg"));
    data = new byte[is.available()];
    is.read(data);
    base64Image = new String(Base64.encode(data));
} catch (Exception e) {
    e.printStackTrace();
} finally {
    if (null != is) {
        try {
            is.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

File file1=new File("D:\ceshi.jpg");
byte[] decoByte=Base64.decode(base64Image);
for (int i = 0; i < decoByte.length; ++i) {
       if (decoByte[i] < 0) {
           decoByte[i] += 256;
       }
}
try {
    FileUtils.writeByteArrayToFile(file1, decoByte);
} catch (IOException e) {
    e.printStackTrace();
}

具体原因待业余时间探索，特此记录